Conventional incandescent bulb-type lamps are currently being replaced by less energy consuming alternatives, such as LED lamps. Important issues in retrofit LED lamp design are to obtain omnidirectional light distribution resembling the light distribution of an incandescent light bulb and to provide sufficient dissipation of heat generated by the LEDs and the driving electronics.
WO 2010/058325 shows a bulb-type LED lamp having a bulb mounted on a socket. Inside the bulb, a plurality of LEDs are mounted on a printed circuit board (PCB), which is connected to cooling means. The cooling means extends from inside the bulb to the outer surface of the bulb, whereby the outer surface of the bulb is formed both by sub-areas of a light transmittable surface and the cooling means. The sub-areas and the cooling means are preferably arranged in an interdigitated (alternating) configuration. The cooling means and the light transmittable surface form the bulb outer surface, thereby improving heat dissipation from the LEDs as well as the omnidirectional light distribution. However, such lamps give rise to new manufacturing challenges due to the more complex interconnection between the driving electronics and the PCBs caused by their mutual orientation.